Metal oxide deposition system

ABSTRACT

A system for distributing silicon dioxide particles produced by a hydrolysis torch over the surface of a deposition mandrel. The system includes a drive mechanism for rotating and translating the mandrel past the torch, a bell crank for pivotally supporting the torch and a lost motion drive link for interconnecting the drive mechanism and the bell crank. As the drive mechanism rotates and translates the mandrel, the drive link and the bell crank move the torch along a line extending parallel to the surface of the mandrel. This assures uniform distribution of the silicon dioxide particles over the surface of the mandrel.

United States Patent 1191 Skooglund, Jr. 14 1 Jan. 30, 1973 [54] METAL OXIDE DEPOSITION SYSTEM 2,316,959 4 1943 Hinkley et al. ..118 321 2,345,834 4/l944 Schweitzer ..l l8/32l [75] lnvenwr' Dallas 2,838,024 6/1958 Rekettye ..118/321 Assignee: Texas Instruments Incorporated 3,] Cserny X Dallas 3,399,649 9/]968 Kidgell et al. ..l 18/47 3,609,829 lO/l97l Carrell et al ..264/81 X [22] Filed: Feb. 19, 1971 Primary ExaminerMorris Kaplan [211 Appl' ll7l50 Att0rneySamuel M. Mins, Jr. et al.

Related US. Application Data [57] ABSTRACT [62] Division of Ser. No. 808,894, March 20, 1969, abandoned A system for distnbutlng s1l1con d1ox1de particles produced by a hydrolysis torch over the surface of a 152 US. Cl ..ll8/47, 118/321 dEPOSifiO" mandrel The System dudes drive 511 1111.01 ..C23c 11/00 mechanism mming and translating the mandrel [58] Field of Search ..1 18/47.? 47.8 321 48- P the a Crank Pivmany SuPPmmg the 219/124 264/81 338 i torch and a lost motion drive link for interconnecting CA 46 6 Z CC 46 i; 46 46 the drive mechanism and the bell crank. As the drive FB 6 F2 PS mechanism rotates and translates the mandrel, the drive link and the bell crank move the torch along a line extending parallel to the surface of the mandrel. [56] References Cited This assures uniform distribution of the silicon dioxide UNITED S AT PATENTS particles over the surface of the mandrel.

2,272,342 2/1942 Hyde ..264/332 UX 6 Claims, 2 Drawing Figures PATENTED JAN 30 I973 ON 55:." m mm, Q m 2 vv vw j 9 wv mm I wk 1 1/ Y wn mv 9 ww mm mu mm v METAL OXIDE DEPOSITION SYSTEM This application is a division of application Ser. No. 808,894, filed Mar. 20,1969, and now abandoned.

This invention relates to the production of metal oxide articles by decomposition of volatile metal chlorides, and more particularly to the formation of metal oxide articles by vapor phase hydrolysis of volatile anhydrous chlorides of metallic elements from Groups III and IV of the periodic system, particularly silicon tetrachloride.

It is necessary in the formation of many semiconductor devices to pull monocrystalline silicon from a melt of very pure silicon. In order to prevent impurities from entering the melt of silicon from the walls of the melt crucible, it has been found advantageous to construct the melt crucible from very pure silica. Further, it has been found desirable to provide the silicon melt crucible with very uniform side walls and with a symmetrical configuration in order to ensure a uniform pull form the silicon melt and in order to prevent collapse of the crucible during the process.

The copending applications entitled Method and Apparatus for Forming an Article of High Purity Metal Oxide by Michael A. Carrell, filed July 11, 1968, Ser. No. 744,188 and now US. Pat. No. 3,565,346 and Production of an Article of High Purity Metal Oxide by Herbert J. Moltzan, filed July 11, 1968, Ser. No. 744,153, and now U.S. Pat. No. 3,565,345 both disclose torches which form metal oxides by vapor phase hydrolysis of volatile metal chlorides. Both applications also disclose a system for forming semiconductor melt crucibles in which a graphite mandrel is rotated and translated past a hydrolysis torch. The metal oxide formed by the torch is deposited on the mandrel to form a melt crucible having the shape of the mandrel. The present invention comprises an improvement over the melt crucible forming system disclosed in the Carrell and Moltzan applications.

In accordance with the present invention, a hydrolysis torch is maintained at a predetermined distance and angle with respect to the deposition surface of a mandrel as the mandrel is rotated and translated past the torch. This results in an even distribution of metal oxide over the deposition surface of the mandrel which in turn results in a melt crucible having a uniform wall thickness. More particularly, the torch is mounted on a lever system that is driven by the mechanism that rotates and translates the mandrel. As the mandrel is rotated and translated, the level system moves the torch along a line extending parallel to the deposition surface of the mandrel.

A more complete understanding of the invention may be had by referring to the following detailed description when taken in conjunction with the drawing, wherein:

FIG. 1 is a side view of a metal oxide deposition system employing the invention in which certain parts have been omitted and certain other parts have been broken away more clearly to illustrate certain features of the invention, and

FIG. 2 is a view similar to FIG. 1 showing the system at a different stage of its operation.

Referring now to the drawings, like reference numerals designate like parts through the several views.

-and a deposition mandrel Referring first to FIG. 1, there is shown a metal oxide deposition system 10 including a hydrolysis torch 12 14. In use, silicon tetrachloride, hydrogen and oxygen are supplied to the torch 12 which in turn forms these materials into si1- icon dioxide and water by vapor phase hydrolysis. Although any hydrolysis torch may be employed, the torch disclosed and claimed in the above-identified Carrell and Moltzan applications is preferred.

The silicon dioxide formed by the torch 12 is deposited on the mandrel 14 to form a silica melt crucible having the shape of the mandrel 14. In order to form symmetrical melt crucibles having side walls of uniform thickness, it is necessary to distribute the silicon dioxide formed by the torch I2 uniformly over the entire surface of the mandrel 14.

The mandrel 14 is rotated and translated past the torch 12 by a mandrel drive mechanism 16. The drive mechanism 16 is supported on a base 18 which in turn supports a fixed plate 20. A threaded block 22 extends vertically upwardly from the fixed plate 20.

A sliding plate 24 is slidably supported on the fixed plate 20 for movement leftwardly and rightwardly with respect to the threaded block 22. The sliding plate 24 supports a bearing block 26 and a motor 28. A lead screw 30 is supported and rotated by the motor 28 and in turn supports the mandrel 14. The lead screw 30 is threadably engaged with the threaded block 22 and is rotatably supported by a bearing (not shown) mounted in the bearing block 26.

The hydrolysis torch 12 is supported on a bell crank 32 which in turn is pivotally supported on a fixed pivot 34. The bell crank 32 includes an upwardly extending arm 36, a downwardly extending arm 38 and an inwardly extending arm 40 which extends inwardly under the mandrel 14 to an arm similar to the arm 38 which in turn extends upwardly to a pivot similar to the pivot 34. The hydrolysis torch 12 is supported on the middle of the inwardly extending arm 40 under the mandrel l4. Pivotal movement of the bell crank 32 about the fixed pivot 34 is limited by an adjustable stop 42.

The bell crank 32 is interconnected with the drive mechanism 16 by a drive link 44. The drive link 44 includes a drive rod 46 which is pivotally connected to the upwardly extending arm 36 of the bell crank 32 by a pin 48. The pin 48 extends into an adjustment slot 50 formed in the arm 36 and is normally secured in such a way that it is prevented from sliding in the slot 50.

The drive link 44 is connected to the drive mechanism 16 by a drive ring 52 which is rotatably secured to the sliding plate 24 and which slidably receives the drive rod 46. A pair of collars 54 and 56 limit sliding motion of the drive rod 46 with respect to the drive ring 52. A spring 58 is positioned on the drive rod 46 between the drive ring 52 and the collar 56.

The operation of the system 10 begins with the sliding plate 24 and the components supported thereby, including the drive ring 52 and the mandrel 14, initially located in the extreme right hand position as shown in FIG. 1. When the components are in the right-hand position, the spring 58 is compressed and the bell crank 32 is accordingly urged tightly against the stop 42.

When power is supplied to the motor 28, the lead screw 30 is rotated. This in turn rotates the mandrel 14 with respect to the hydrolysis torch 12. Since the lead screw 30 is threadably engaged with the threaded block 22, rotation of the lead screw 30 causes the lead screw 30 to move to the left. Since the lead screw 30 is supported by the motor 28 and the bearing block 26, and since the motor 28 and the bearing block 26 are supported on the sliding block 24, this drives the sliding block 24 to the left with respect to the fixed block 20. Leftward movement of the lead screw 30 and of the sliding block 24 results in leftward movement of the mandrel 14 with respect to the torch 12 and leftward movement of the drive ring 52 .with respect to the drive rod 46.

Leftward movement of the drive ring 52 gradually reduces the compression of the spring 58. The spring 58 is, however, sufficiently preloaded to maintain the bell crank 32 in engagement with the adjustable stop 42 until the drive ring 52 engages the collar 54. When the drive ring 52 engages the collar 54, the drive rod 46 is pulled toward the base 18 which in turn pivots the bell crank 32 counterclockwise about the fixed pivot at 34.

The components of the system are so constructed that the beginning of the curved right-hand end of the mandrel 14 is positioned above the torch 12 when the drive ring 52 engages the collar 54. Then, as the curved portion of the mandrel 14 is moved past the pivot 34, the drive link 44pivots the bell crank 32 about the fixed pivot 34. This causes the torch 12 to move along a line extending parallel to the surface of the mandrel 14 as the mandrel 14 continues to move leftwardly.

Rotation of the lead screw 30 in the threaded block 22 continues until the sliding block 24 and the components positioned thereon, particularly the drive ring 52 and the mandrel 14, are in the extreme left-hand position shown in FIG. 2. At this point, the bell crank 32 is fully pivoted into an extreme position and the hydrolysis torch 12 is aligned with the end of the man drel 14.

As soon as the component parts of the system 10 have reached the position shown in FIG. 2, a limit switch (not shown) causes the motor 28 to reverse the direction of rotation of the lead screw 30. This causes the sliding plate 24 and the components supported thereon to move back toward the right-hand position shown in FIG. 1. During this movement, the mandrel 14 is, of course, continuously rotated and is simultaneously translated to the right.

Upon rightward movement of the sliding plate 24, the drive ring 52 applies force to the bell crank 32 through the spring 58. This immediately begins to pivot the bell crank 32 about the pivot 34 in a clockwise direction. The bell crank 32 continues to pivot until the downwardly extending arm 38 engages the adjustable stop 42.

The component parts of system 10 are so constructed that the arm 38 of the bell crank 32 engages the stop 42 just as the straight portion of the mandrel 14 comes into alignment with the pivot 34. Because it is attached to the plate 24, the drive ring 52 continues to move ri ghtwardly after engagement of the bell crank 32 with the stop 42. This motion, however, is absorbed by the spring 58. Thus, the torch 52 remains in a fixed position during the translation of the straight portion of the mandrel 14 past the torch 12.

When the sliding plate 24 reaches the position shown in FIG. 1, a second limit switch (not shown) causes the motor 28 again to reverse the direction of rotation of the lead screw 30. This causes the mandrel 14 again to move from right to left. The system 10 is operated through as many operating cycles, each including movement from the extreme right-hand position to the extreme left-hand position and back, as is necessary to build the layer of silicon dioxide on the mandrel 14 to a desired thickness.

The metal deposition system shown in the drawing is superior to prior systems principally because it operates to move a hydrolysis torch along a line extending parallel to the deposition contour of a deposition mandrel. This action maintains the torch at the same distance from and at the same angle with respect to the deposition surface of the mandrel throughout the deposition process. This in turn results in an extremely uniform distribution of silicon dioxide particles over the entire surface of the mandrel, a result which has not been possible in deposition systems provided heretofore.

Although only one embodiment of the invention has been shown in the drawing and described in the foregoing specification, it will be understood that the invention is not limited to the embodiment disclosed but is capable of rearrangement, modification ad substitution of the parts and elements without departing from the spirit of the invention.

What is claimed is:

l. A metal oxide deposition system including:

a deposition mandrel having a predetermined deposition contour;

a torch for depositing metal oxide on the deposition contour of the mandrel;

means for moving the mandrel and the torch relative to each other so that the torch distributes metal oxide over the entire deposition contour of the mandrel, and

means responsive to relative movement between the mandrel and the torch for maintaining the torch on a line extending substantially parallel to the contour of the mandrel during the relative movement so that the torch distributes metal oxide evenly over the entire deposition contour.

2. The metal oxide deposition system according to claim 1 wherein the means for maintaining the torch on a line extending parallel to the contour of the mandrel maintains the torch at the same distance from and at the same angle with respect to the mandrel during the entire relative movement.

3. The metal oxide deposition system according to claim 1 wherein the means for maintaining the torch on a line extending parallel to the contour of the mandrel is driven by the relative moving means and operates to move the torch whenever the relative moving means positions a curved portion of the deposition contour adjacent the torch and to maintain the torch stationary whenever the relative moving means positions a straight portion of the deposition contour adjacent the torch.

4. A silica deposition system including: a deposition mandrel having a curved deposition surface; a hydrolysis torch for depositing silica on the deposition surface;

means for moving the mandrel relative to the torch so that the torch distributes silica over the entire deposition surface, and

a system for supporting the torch and for moving the torch along a path extending parallel to the deposition surface as the mandrel moves relative to the torch.

S. The silica deposition system according to claim 4 wherein the system includes a pivotally supported lever l0 

1. A metal oxide deposition system including: a deposition mandrel having a predetermined deposition contour; a torch for depositing metal oxide on the deposition contour of the mandrel; means for moving the mandrel and the torch relative to each other so that the torch distributes metal oxide over the entire deposition contour of the mandrel, and means responsive to relative movement between the mandrel and the torch for maintaining the torch on a line extending substantially parallel to the contour of the mandrel during the relative movement so that the torch distributes metal oxide evenly over the entire deposition contour.
 2. The metal oxide deposition system according to claim 1 wherein the means for maintaining the torch on a line extending parallel to the contour of the mandrel maintains the torch at the same distance from and at the same angle with respect to the mandrel during the entire relative movement.
 3. The metal oxide deposition system according to claim 1 wherein the means for maintaining the torch on a line extending parallel to the contour of the mandrel is driven by the relative moving means and operates to move the torch whenever the relative moving means positions a curved portion of the deposition contour adjacent the torch and to maintain the torch stationary whenever the relative moving means positions a straight portion of the deposition contour adjacent the torch.
 4. A silica deposition system including: a deposition mandrel having a curved deposition surface; a hydrolysis torch for depositing silica on the deposition surface; means for moving the mandrel relative to the torch so that the torch distributes silica over the entire deposition surface, and a system for supporting the torch and for moving the torch along a path extending parallel to the deposition surface as the mandrel moves relative to the torch.
 5. The silica deposition system according to claim 4 wherein the system includes a pivotally supported lever for supporting the torch and a drive link interconnecting the relative moving means and the lever for pivoting the ever and thereby moving the torch along a path extending parallel to the deposition surface. 